In gas turbine engines, compressed air discharged from a compressor section and fuel introduced from an external source are mixed together and burned in a combustors of a combustion section. The mixture is directed through a turbine section, where the mixture expands to provide rotation of a turbine rotor. The turbine rotor may be linked to an electric generator, wherein the rotation of the turbine rotor can be used to produce electricity in the generator.
Gas turbine engines are known to produce an exhaust stream containing a number of combustion products. Many of these byproducts of the combustion process are considered atmospheric pollutants, and increasingly stringent regulations have been imposed on the operation of gas turbine power plants in an effort to minimize the production of these gasses. Of particular concern is the regulation of the production of the various forms of nitrogen oxides collectively known as NOx. It is known that NOx emissions from a gas turbine increase significantly as the combustion temperature rises. One method of limiting the production of NOx is the use of a lean mixture of fuel and combustion air, i.e. a relatively low fuel-to-air ratio, thereby limiting the peak combustion temperature to a level below the threshold for NOx production. However, higher combustion temperatures are desirable to obtain higher efficiency and reduced production of carbon monoxide.
Gas turbine engines have been designed to combust a broad range of hydrocarbon fuels, such as natural gas, kerosene, biomass gas, etc, and more recently gas turbines engines have been designed to combust syngas produced from integrated gasification combined cycle applications. The syngas has a much higher flame speed than natural gas and may be more susceptible to flame flashback when applied in a combustion section. Flame flashback in the combustion section of gas turbine engines is undesirable, as it can cause damage to the components in and around the combustors, i.e., the flame may anchor onto the components and may burn through them.
Specifically, flame flashback may be caused when the turbulent burning velocity of the air and fuel mixture exceeds the axial flow velocity in the combustor, especially in low velocity regions. Flame flashback can also occur in recirculation zones that are caused by abrupt changes in the area of the flow path of the air and fuel mixture, such as at an aft end of a swirler assembly of a fuel injection system, which provides an exit for the air and fuel mixture from the fuel injection system into a main combustion chamber.